This invention relates to packaging apparatus, and more particularly to so-called sleeve wrapping apparatus for sleeve wrapping products in heat-shrinkable film for subsequent shrinking in a shrink tunnel.
The invention is especially concerned with apparatus of a type heretofore sold by the assignee of this application known as a "sleeve wrapper" in which a unit to be wrapped is fed forward by a conveyor against a vertical reach of film comprising a first web issuing from an upper roll and extending downwardly and a second web issuing from a lower roll and extending upwardly with the ends of the two webs heat-sealed together. As the unit moves forward, the upper web is draped over the unit and the lower web is draped under it. The unit then dwells in place while a pair of seal bars are closed behind the unit to heat-seal the two webs together on the trailing side of the unit and to sever the webs through the seal so as to provide a trailing seal for the film draped around the unit to form a sleeve, and a seal constituting the leading seal for the next sealing operation. After the sealing operation, the bars are opened and the enwrapped unit is fed forward away from the webs and another unit fed forward for being wrapped.
Reference may be made to my coassigned copending application Ser. No. 435,731, filed Jan. 23, 1974, now U.S. Pat. No. 3,927,507, showing a development in sleeve wrappers involving the provision of a drive for the conveyor of the wrapper adapted to effect smooth starting and stopping of the conveyor so as to enable handling of units of relatively low stability (e.g., filled bags) without the units tipping over or becoming disoriented while wrapping the units at commercially necessary speeds (e.g., up to 30-40 cycles per minute). While the sleeve wrapper shown in said application Ser. No. 435,731 is quite satisfactory for wrapping single items (which may be of low stability, such as a filled bag standing upright), it is not always satisfactory for wrapping a unit which comprises a plurality of products each of which may be of low stability, such as a plurality of cans (e.g., two dozen loose cans standing upright arranged in a four-by-six array, or four six-packs of cans arranged in a two-by-two array) unless the products making up the unit are packaged in a tray before being wrapped and then wrapped with the tray. This problem is encountered not only with loose cans, for example, but also with six-packs of cans in which the six cans are held together by an apertured sheet plastic carrier of the type known as the HICONE carrier (for which reference may be made to U.S. Pat. No. 2,874,835). Even with such a carrier, in wrapping six-packs with the sleeve wrapper of the aforesaid application Ser. No. 435,731, the cans may angle outwardly away from one another or the packs may become separated, unless confined by a tray.